Direct-current side secondary power suppression method for three-phase PWM (Pulse-Width Modulation) rectifier

Abstract

The invention provides a direct current side secondary power suppression method for a three-phase PWM rectifier, and belongs to the field of power electronics. The method is applied to a three-phase PWM rectifier. The method comprises the following steps: connecting a DC-DC converter, an H bridge, an LC filter circuit and a sampling resistor # imgabs0 # in parallel at the direct current side of a three-phase PWM rectifier to form an active negative capacitance circuit; the active negative capacitor circuit is connected in series with a first capacitor # imgabs1 # to obtain a capacitor series equivalent circuit based on the active negative capacitor; voltage signals are sampled on the direct current side of the three-phase PWM rectifier and connected to the input end of the digital signal controller, the digital signal controller outputs signals to control the H bridge, capacitance of the active negative capacitance circuit is changed, and finally secondary power suppression on the direct current side of the three-phase PWM rectifier is achieved. According to the invention, a large capacitance value can be realized by using a small volume, the realized capacitance equivalent circuit has the characteristic of adjustable capacitance value, and different capacitance values can be flexibly selected according to different three-phase PWM rectifier direct current side voltage double frequency suppression requirements.

Description

Technical Field

[0001] The invention belongs to the field of power electronics, and in particular relates to a method for suppressing secondary power on the DC side of a three-phase PWM rectifier. Background Art

[0002] With the rapid development of distributed power generation systems, three-phase pulse width modulation (PWM) converters are widely used in various power electronics fields due to their advantages such as adjustable power factor, adjustable AC current amplitude, and adjustable DC bus voltage.

[0003] However, three-phase PWM converters can only have high performance output when operating under balanced conditions. Unlike stable large-scale power grids, weak grid systems such as distributed generation systems generally face three-phase unbalanced conditions, which may trip sensitive loads and thus degrade system performance. When the converter is under unbalanced conditions, some problems may occur, such as DC bus fluctuations, AC current distortion and imbalance, and power oscillation.

[0004] In order to solve these problems, a power decoupling circuit can be added to bypass high-frequency energy, thereby suppressing the double frequency fluctuation of the DC side output voltage of the three-phase inverter. Power decoupling can be divided into two categories: one is passive power decoupling by directly connecting a traditional capacitor or LC resonant circuit in parallel on the DC side; the other is active power decoupling by adding an active power decoupling circuit on the basis of a conventional three-phase converter. The passive power decoupling scheme using traditional capacitors requires a large capacitance value in order to obtain the ideal double frequency suppression effect, which results in the volume of the traditional capacitors used being very large. With the introduction of large-value capacitors, the passive power decoupling method will reduce the power density of the PWM rectifier. At the same time, the bulky electrolytic capacitors also have a negative impact on the reliability and service life of the rectifier.

[0005] The active power decoupling method with an active power decoupling circuit only requires a number of switching devices and necessary supporting capacitors and filter circuits to achieve a good DC side voltage double frequency fluctuation suppression effect, and the volume and service life have been greatly improved. However, most of the existing active power decoupling technologies (Active Power Decoupling, APD for short) require AC sampling to calculate the secondary power, and then control the active power decoupling circuit on the DC side accordingly; and the suppression effect of APD on the DC side secondary power is not adjustable and cannot be flexibly adjusted according to different occasions. Summary of the invention

[0006] The object of the present invention is to provide a method for suppressing secondary power on the DC side of a three-phase PWM rectifier, so as to solve the technical problems that the secondary power suppression method in the prior art is realized by increasing the capacitor on the DC side of the rectifier, which is bulky and the capacitance value cannot be adjusted.

[0007] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows: A method for suppressing secondary power on the DC side of a three-phase PWM rectifier, the method being applied to the three-phase PWM rectifier; the method comprising: ,negative electrode The two ends are connected in parallel to the input end of the DC-DC converter, and the output end of the DC-DC converter is connected to the first switch tube. , the second switch tube , the third switch tube , the fourth switch tube The H-bridge structure formed; the DC-DC converter and the H-bridge structure constitute a single-phase inverter; the DC-DC converter takes power from the DC bus as the DC power supply of the single-phase inverter; the output end of the single-phase inverter is connected to a filter capacitor , filter inductor The LC filter circuit is composed of a sampling resistor connected in series with the output end of the single-phase inverter after the LC filter circuit. After the first capacitor Connect in series and then in parallel to the positive pole of the DC side of the three-phase PWM rectifier ,negative electrode Two ends; single-phase inverter, filter capacitor And filter inductor LC filter circuit and sampling resistor An active negative capacitance circuit is formed; the active negative capacitance circuit and the first capacitor The capacitor series equivalent circuit based on active negative capacitance is obtained by connecting in series; the second capacitor ,load Connect in parallel to the positive pole of the DC side of the three-phase PWM rectifier ,negative electrode Both ends; on the positive pole of the DC side of the three-phase PWM rectifier ,negative electrode The voltage signal is sampled at both ends and connected to the input end of the digital signal controller, and the output end of the digital signal controller is connected to the first switch tube of the single-phase inverter. , the fourth switch tube The output end of the digital signal controller is connected to the second switch tube of the single-phase inverter after passing through the inverter. , the third switch tube ; The digital signal controller outputs a signal to the first switch tube , the second switch tube , the third switch tube , the fourth switch tube By controlling the active negative capacitor circuit, the capacitance of the active negative capacitor circuit is changed, and then the capacitor series equivalent circuit based on the active negative capacitor is changed, and finally the secondary power suppression on the DC side of the three-phase PWM rectifier is achieved.

[0008] Furthermore, the first switch tube With the third switch The collector of the second switch is connected to the positive output terminal of the DC-DC converter. With the fourth switch The emitter of the first switch is connected to the negative output terminal of the DC-DC converter; The emitter of the second switch tube The collector of the filter inductor is connected to One end of the filter inductor The other end is connected to the filter capacitor One end of the third switch tube The emitter of the fourth switch tube The collector of the The other end of the filter capacitor and filter inductor Constitute an LC low-pass filter structure; resistor One end of the filter capacitor , filter inductor The points that are connected are connected; resistance The other end is connected to the first capacitor One end of the first capacitor The other end is connected to the positive electrode of the DC side of the three-phase PWM rectifier ; Filter capacitor Connect to the third switch The emitter of the fourth switch tube One end of the collector is connected to the negative electrode of the DC side of the three-phase PWM rectifier .

[0009] Furthermore, the output terminal of the digital signal controller is connected to the first switch tube And the fourth switch The gate of the digital signal controller is connected to the inverter. Then connected to the second switch With the third switch of the gate.

[0010] Furthermore, the digital signal controller samples the DC side voltage of the three-phase rectifier , that is, the positive electrode on the DC side of the three-phase PWM rectifier With negative electrode The voltage between the two is sent to the digital signal controller; the digital signal controller converts the DC side voltage of the three-phase rectifier The voltage signal with a specific frequency of 100Hz is obtained by separation through the phase-locked loop PLL and multiplied by the voltage division coefficient Get the terminal voltage of the active negative capacitance circuit , and then the terminal voltage of the active negative capacitor circuit Multiply by the inverse of the sampling factor Get the node voltage ; and the node voltage Multiply by the constant term frequency-capacitance coefficient , The differential multiplied by the differential term frequency-capacitance coefficient , the two are added to get the modulated signal ; Finally, the modulated signal and carrier signal The square wave signal is sent to the comparator and is the output signal of the digital signal controller, that is, the first switch tube , the fourth switch tube The gate control signal is passed through the inverter to obtain the second switch tube , the third switch tube The gate control signal is applied to the first switch tube , the second switch tube , the third switch tube , the fourth switch tube The control changes the output of the H-bridge, making the active negative capacitor circuit exhibit capacitor port characteristics with different capacitance values.

[0011] Compared with the prior art, the present invention has the following beneficial technical effects: 1) The present invention adds positive and negative capacitors in series to the DC side, so that a large capacitance value can be achieved with a very small volume. The realized capacitor equivalent circuit has the characteristic of adjustable capacitance value, and different capacitance values ​​can be flexibly selected according to different requirements for double frequency suppression of the DC side voltage of the three-phase PWM rectifier.

[0012] 2) The sampling signal of the control part of the present invention comes directly from the DC side and does not involve the sampling and calculation of the AC measurement, so it can be directly installed at any position on the DC side.

[0013] 3) The DC source of the single-phase inverter part of the present invention is provided by a DC-DC module connected to a DC bus conversion output, and no additional DC voltage source is required. It can adapt to different power occasions. Compared with the traditional active power decoupling circuit, the withstand voltage value of the switch tube is also reduced, which is beneficial to prolonging the service life.

[0014] 4) The basic capacitance equivalent principle of the present invention is the series connection between positive and negative capacitors, so theoretically, a capacitance range of zero to infinity can be equivalently obtained by using an electrolytic capacitor of a certain size. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0016] Figure 1 This is a structural diagram of the secondary power suppression circuit on the DC side of the three-phase rectifier of the present invention.

[0017] Figure 2 It is a control flow chart of the equivalent capacitance circuit based on active negative capacitance of the present invention.

[0018] Figure 3 The waveform of the DC side load secondary power suppression effect when the active negative capacitor value is -900uF simulated by the present invention.

[0019] Figure 4 The waveform of the DC side load secondary power suppression effect when the active negative capacitor value is -800uF simulated by the present invention. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] The method for suppressing the secondary power on the DC side of a three-phase PWM rectifier proposed in the present invention is based on the following principle of making the circuit topology have the port characteristics of a capacitor with adjustable capacitance. For a positive capacitor, the relationship between its voltage and current can be expressed by the following first-order differential relationship:

[0022] in, is the voltage across the positive capacitor, is the current flowing through the positive capacitor, is the capacitance of the positive capacitor.

[0023] For negative capacitance, its DC characteristics are consistent with traditional positive capacitance, showing that it blocks DC current, and its AC characteristics are similar to those of inductance. Therefore, the relationship between the current and voltage of negative capacitance can be described by first-order calculus:

[0024] in, is the voltage across the negative capacitor, is the current flowing through the negative capacitor, is the capacitance of negative capacitor, which is a negative number. To take the absolute value.

[0025] According to the equivalent capacitance calculation formula of positive and negative capacitors in series:

[0026] in, It is the equivalent capacitance of positive and negative capacitors connected in series.

[0027] From the calculation formula of equivalent capacitance of positive and negative capacitors in series, we know that when a positive capacitor is connected in series with a negative capacitor, and the capacitance of the positive capacitor is set to a certain value, the equivalent capacitance of the capacitors in series is affected by the ratio of the absolute values ​​of the positive and negative capacitances: the closer the absolute values ​​of the positive and negative capacitances are, the greater the equivalent capacitance of the capacitors in series. Therefore, by changing the capacitance of the negative capacitor, the equivalent capacitance of the capacitors in series can be adjusted.

[0028] For a three-phase PWM rectifier under unbalanced working conditions, there is a double frequency fluctuation of power on the DC side, that is, the power on the DC side is mainly composed of a DC component and a double frequency AC component. Due to the characteristics of capacitors passing AC and blocking DC, the capacitor connected in parallel on the DC side can provide a path for the AC component of power, so that very little AC energy flows through the load on the DC side. Obviously, the higher the DC side capacitance is set, the less the capacitor branch connected in parallel on the DC side will hinder the AC component of power, so that the DC side load has less AC energy.

[0029] Based on the above principle, the present invention provides a method for suppressing the secondary power on the DC side of a three-phase PWM rectifier, which is applied to the three-phase PWM rectifier. Figure 1 As shown, the method includes: at the positive electrode of the DC side of the three-phase PWM rectifier ,negative electrode The two ends are connected in parallel to the input end of the DC-DC converter, and the output end of the DC-DC converter is connected to the first switch tube. , the second switch tube , the third switch tube , the fourth switch tube The H-bridge structure is formed. The DC-DC converter and the H-bridge structure form a single-phase inverter. The DC-DC converter takes power from the DC bus as the DC power supply for the single-phase inverter. The output of the single-phase inverter is connected to a filter capacitor. , filter inductor The output of the single-phase inverter after the LC filter circuit is connected in series with a sampling resistor After the first capacitor Connect in series and then in parallel to the positive pole of the DC side of the three-phase PWM rectifier ,negative electrode Both ends. Single-phase inverter, filter capacitor And filter inductor LC filter circuit and sampling resistor The active negative capacitance circuit is formed. The active negative capacitance circuit and the first capacitor The series connection results in a capacitor series equivalent circuit based on active negative capacitance. ,load Connect in parallel to the positive pole of the DC side of the three-phase PWM rectifier ,negative electrode Both ends. The positive pole on the DC side of the three-phase PWM rectifier ,negative electrode The voltage signal is sampled at both ends and connected to the input end of the digital signal controller, and the output end of the digital signal controller is connected to the first switch tube of the single-phase inverter. , the fourth switch tube The output end of the digital signal controller is connected to the second switch tube of the single-phase inverter after passing through the inverter. , the third switch tube The digital signal controller outputs a signal to the first switch tube. , the second switch tube , the third switch tube , the fourth switch tube By controlling the active negative capacitor circuit, the capacitance of the active negative capacitor circuit is changed, and then the capacitor series equivalent circuit based on the active negative capacitor is changed, and finally the secondary power suppression on the DC side of the three-phase PWM rectifier is achieved.

[0030] The first switch With the third switch The collector of the second switch is connected to the positive output terminal of the DC-DC converter. With the fourth switch The emitter of the first switch is connected to the negative output terminal of the DC-DC converter. The emitter of the second switch tube The collector of the filter inductor is connected to One end of the filter inductor The other end is connected to the filter capacitor One end of the third switch tube The emitter of the fourth switch tube The collector of the The other end of the filter capacitor and filter inductor This constitutes an LC low-pass filter structure. One end of the filter capacitor , filter inductor The points that are connected are connected. The other end is connected to the first capacitor One end of the first capacitor The other end is connected to the positive electrode of the DC side of the three-phase PWM rectifier . Filter capacitor Connect to the third switch The emitter of the fourth switch tube One end of the collector is connected to the negative electrode of the DC side of the three-phase PWM rectifier .

[0031] The output terminal of the digital signal controller is connected to the first switch tube And the fourth switch The gate of the digital signal controller is connected to the inverter. Then connected to the second switch With the third switch of the gate.

[0032] The following briefly describes a method for suppressing the secondary power on the DC side of a three-phase PWM rectifier based on the principle of making the circuit topology have the port characteristics of a capacitor with adjustable capacitance and a capacitor series equivalent circuit based on active negative capacitance proposed by the method of the present invention.

[0033] For an active negative capacitor, the voltage-current relationship at its port can be expressed in the S domain as follows:

[0034] in, is the current flowing through the active negative capacitance circuit, is the terminal voltage of the active negative capacitance circuit, is the absolute value of the active negative capacitance, is the Laplace operator.

[0035] For the structure where positive and negative capacitors are connected in series, the voltage division relationship between the two can be derived:

[0036] in, is the voltage on the DC side of the three-phase rectifier, Indicates the capacitance of the positive capacitor, i.e. the first capacitor The capacitance value, is the voltage division coefficient of the active negative capacitor for the entire positive and negative capacitor series structure.

[0037] Based on Kirchhoff's voltage and current laws, as well as the port characteristics of inductance and capacitance, the following expressions can be written:

[0038]

[0039] in, is the filter capacitor value, is the current flowing through the filter capacitor, is the filter inductance value, is the output voltage of the single-phase inverter before being processed by the filter circuit, is the resistance of the sampling resistor in the active negative capacitance circuit.

[0040] Through the above formula, the following relationship can be obtained:

[0041] Transforming formula (8) to the time domain, we can get the following expression:

[0042] in, is the time domain expression of the DC side voltage of the three-phase rectifier, is the time domain expression of the output voltage of the single-phase inverter.

[0043] Since the single-phase inverter output voltage The modulation signal inside the digital signal controller The phase is the same and the amplitude is proportional, so the output signal of the digital signal controller is:

[0044] in, is the output voltage of the digital signal controller, It is the inverse of the sampling factor of the digital signal controller.

[0045] The terminal voltage of the active negative capacitance circuit is expressed as follows:

[0046] in, The time domain expression for the port voltage of the active negative capacitance circuit is, represents the inverse Laplace operation, Represents the amplitude of the port voltage signal of the active negative capacitance circuit, Represents the angular frequency of the port voltage signal of the active negative capacitance circuit.

[0047] The voltage division coefficient of the active negative capacitor for the entire positive and negative capacitor series structure has the following relationship:

[0048] Substituting formula (11) and (12) into formula (10), we can get the relationship between the sampling signal and the modulation signal:

[0049] in, represents the constant term frequency-capacitance coefficient, let ; represents the differential term frequency-capacitance coefficient, let , then formula (12) can be simplified to:

[0050] From formula (14), we can see that by changing the voltage divider coefficient , constant term frequency-capacitance coefficient and differential term frequency-capacitance coefficient It can change the modulation signal of the digital signal controller, thereby changing the output voltage of the digital signal controller, and controlling the first switch tube , the second switch tube , the third switch tube , the fourth switch tube , changing the output of the H-bridge, causing the capacitance of the active negative capacitor circuit to change. Voltage division coefficient The setting is determined by the target active negative capacitor value. Adjustment; Constant term frequency-capacitance coefficient and differential term frequency-capacitance coefficient The change in the angular frequency of the port voltage signal through the active negative capacitance circuit And the capacitance of the active negative capacitor Adjustment.

[0051] According to the calculation of the equivalent capacitance of the capacitors in series, by changing the capacitance of the active negative capacitor, the equivalent capacitance of the capacitors in series can be adjusted. The closer the absolute values ​​of the positive and negative capacitances are, the larger the equivalent capacitance of the capacitors in series is, making the equivalent circuit of the capacitors in series equivalent to a large capacitor with adjustable capacitance, thereby achieving secondary power suppression on the DC side of the three-phase PWM rectifier. Based on the conversion relationship of the output signal of the digital signal controller mentioned above, combined with Figure 2 , the secondary power suppression process of the DC side of the three-phase PWM rectifier is explained.

[0052] When working, the digital signal controller samples the DC side voltage of the three-phase rectifier , that is, the positive electrode on the DC side of the three-phase PWM rectifier With negative electrode The voltage between the two is sent to the digital signal controller. The digital signal controller converts the DC side voltage of the three-phase rectifier The voltage signal with a specific frequency of 100Hz is obtained by separation through the phase-locked loop PLL and multiplied by the voltage division coefficient Get the terminal voltage of the active negative capacitance circuit , and then the terminal voltage of the active negative capacitor circuit Multiply by the inverse of the sampling factor Get the node voltage . And the node voltage Multiply by the constant term frequency-capacitance coefficient , The differential multiplied by the differential term frequency-capacitance coefficient , the two are added to get the modulated signal Finally, the modulated signal and carrier signal The square wave signal is sent to the comparator and is the output signal of the digital signal controller, that is, the first switch tube , the fourth switch tube The gate control signal is passed through the inverter to obtain the second switch tube , the third switch tube The gate control signal is applied to the first switch tube , the second switch tube , the third switch tube , the fourth switch tube The control changes the output of the H-bridge, making the active negative capacitor circuit exhibit capacitor port characteristics with different capacitance values.

[0053] Based on the above circuit topology, its control method and working principle are briefly described: Through the circuit structure and control strategy described in the previous article, an active negative capacitor with adjustable capacitance can be obtained, which is connected in series with an ideal positive capacitor, so that the entire branch is equivalent to a large capacitor with adjustable capacitance.

[0054] The branch is running and samples the DC side voltage of the three-phase rectifier As the input signal, the signal obtained after being processed by the digital signal controller and the signal obtained after being inverted by the inverter are used to drive the single-phase inverter H bridge. By adjusting the parameters of the transfer function to change the output of the H bridge, the entire additional circuit containing the source negative capacitor can show the characteristics of the capacitor port with different capacitance values, so that the purpose of using the additional circuit to replace the traditional capacitor with the same capacitance value can be achieved, which provides a path for the double frequency energy, realizes power decoupling, and suppresses the double frequency fluctuation of the DC side voltage of the three-phase PWM rectifier.

[0055] Taking the case of phase C voltage drop as an example, the effect of the present invention on suppressing the secondary power fluctuation on the DC side is as follows: Figure 3-4 The parameters of the power grid, negative capacitance circuit, etc. are shown in Table 1.

[0056] Table 1 is a table of some parameters of the power grid, negative capacitance circuit, etc.

[0057] according to Figure 1 and Figure 2 Build a simulation module in MATLAB, set the preset control parameters according to Table 1, and start running the simulation. First, do not connect the circuit containing the source negative capacitor to the DC side, and observe the voltage double frequency fluctuation. Figure 3-4 As shown, it can be seen that the DC side load power waveform shows a double frequency fluctuation. At t=0.25s, the circuit containing the source negative capacitor is connected in parallel to the DC side.

[0058] According to the two sets of positive capacitors given in Table 2 The capacitance and the equivalent capacitance of the negative capacitance circuit are simulated respectively, and the corresponding Figure 3-4 The DC side power waveform is shown.

[0059] Table 2 Positive capacitance Capacitance and negative capacitance circuit equivalent capacitance simulation table

[0060] The system operation process is as follows: The system samples the DC side voltage of the three-phase rectifier, obtains the 100Hz component through PLL, and obtains the signal wave through calculation. After comparing it with the carrier wave of a certain frequency, it is used to control the switch tube. In order to make the circuit containing source negative capacitance equivalent to capacitors of different capacitance values, so as to obtain different suppression effects, the parameters can be adjusted. , which is the absolute value of the active negative capacitance.

[0061] Depend on Figure 3The overall simulation waveform shows that the added equivalent capacitor circuit containing source negative capacitance can provide a high-frequency path for the energy of the double frequency of the power frequency, consume the double frequency energy in the branch containing source negative capacitance, and effectively suppress the double frequency fluctuation of the DC side voltage. Figure 3-4 It can be seen that with the increase of the equivalent capacitance of the entire branch, the suppression effect of the secondary power becomes better, which also proves the correctness of the adjustable suppression effect of the method proposed in the present invention.

[0062] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A method for suppressing secondary power on the DC side of a three-phase PWM rectifier, characterized in that: The method is applied to a three-phase PWM rectifier; the method comprises: ,negative electrode The two ends are connected in parallel to the input end of the DC-DC converter, and the output end of the DC-DC converter is connected to the first switch tube. , the second switch tube , the third switch tube , the fourth switch tube The H-bridge structure formed; The DC-DC converter and H-bridge structure form a single-phase inverter; The DC-DC converter takes power from the DC bus as the DC power supply for the single-phase inverter; the output end of the single-phase inverter is connected to a filter capacitor , filter inductor The LC filter circuit is composed of a sampling resistor connected in series with the output end of the single-phase inverter after the LC filter circuit. After the first capacitor Connect in series and then in parallel to the positive pole of the DC side of the three-phase PWM rectifier ,negative electrode Two ends; single-phase inverter, filter capacitor And filter inductor LC filter circuit and sampling resistor An active negative capacitance circuit is formed; the active negative capacitance circuit and the first capacitor The capacitor series equivalent circuit based on active negative capacitance is obtained by connecting in series; the second capacitor ,load Connect in parallel to the positive pole of the DC side of the three-phase PWM rectifier ,negative electrode Both ends; on the positive pole of the DC side of the three-phase PWM rectifier ,negative electrode The voltage signal is sampled at both ends and connected to the input end of the digital signal controller, and the output end of the digital signal controller is connected to the first switch tube of the single-phase inverter. , the fourth switch tube The output end of the digital signal controller is connected to the second switch tube of the single-phase inverter after passing through the inverter. , the third switch tube ; The digital signal controller outputs a signal to the first switch tube , the second switch tube , the third switch tube , the fourth switch tube By controlling the active negative capacitor circuit, the capacitance of the active negative capacitor circuit is changed, and then the capacitor series equivalent circuit based on the active negative capacitor is changed, and finally the secondary power suppression on the DC side of the three-phase PWM rectifier is achieved.

2. The method for suppressing secondary power on the DC side of a three-phase PWM rectifier according to claim 1, characterized in that: The first switch With the third switch The collector of the second switch is connected to the positive output terminal of the DC-DC converter. With the fourth switch The emitter of the first switch tube is connected to the negative output terminal of the DC-DC converter; The emitter of the second switch tube The collector of the filter inductor is connected to One end of the filter inductor The other end is connected to the filter capacitor One end of the third switch tube The emitter of the fourth switch tube The collector of the The other end of the filter capacitor and filter inductor Constitute an LC low-pass filter structure; resistor One end of the filter capacitor , filter inductor The points that are connected are connected; resistance The other end is connected to the first capacitor One end of the first capacitor The other end is connected to the positive electrode of the DC side of the three-phase PWM rectifier ; Filter capacitor Connect to the third switch The emitter of the fourth switch tube One end of the collector is connected to the negative electrode of the DC side of the three-phase PWM rectifier .

3. The method for suppressing secondary power on the DC side of a three-phase PWM rectifier according to claim 2, characterized in that: The output terminal of the digital signal controller is connected to the first switch tube And the fourth switch The gate of the digital signal controller is connected to the inverter. Then connected to the second switch With the third switch of the gate.

4. The method for suppressing secondary power on the DC side of a three-phase PWM rectifier according to claim 3, characterized in that: The digital signal controller samples the DC side voltage of the three-phase rectifier , that is, the positive electrode on the DC side of the three-phase PWM rectifier With negative electrode The voltage between the two is sent to the digital signal controller; the digital signal controller converts the DC side voltage of the three-phase rectifier The voltage signal with a specific frequency of 100Hz is obtained by separation through the phase-locked loop PLL and multiplied by the voltage division coefficient Get the terminal voltage of the active negative capacitance circuit , and then the terminal voltage of the active negative capacitor circuit Multiply by the inverse of the sampling factor Get the node voltage ; and the node voltage Multiply by the constant term frequency-capacitance coefficient , The differential multiplied by the differential term frequency-capacitance coefficient , the two are added to get the modulated signal ; Finally, the modulated signal and carrier signal The square wave signal is sent to the comparator and is the output signal of the digital signal controller, that is, the first switch tube , the fourth switch tube The gate control signal is passed through the inverter to obtain the second switch tube , the third switch tube The gate control signal is applied to the first switch tube , the second switch tube , the third switch tube , the fourth switch tube The control changes the output of the H-bridge, making the active negative capacitor circuit exhibit capacitor port characteristics with different capacitance values.

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